Mate in 3

Solution: 1.Ke2 pins the rook and threatens 2.Be1 and 3.Qg3. If 2...Se4 3.Qxe3 or 2...Bxd3+ 3.Sxd3. 1...c4 unpins the rook, which then repins itself by 2.Rxe3 (threat 3.Qg3), leading to a second unpin 2...Se4 3.Rf3 or 2...Rxe3+ 3.Qxe3. The rook can defend by vacating e5. 1...Re7 prevents the knight reaching e7,and White continues 2.gxh8S, threatening 3.Sg6 (2...Rg7 3.Qxe3). 1...Re8 is a critical move allowing the same continuation, since 2...Se7 will interfere with the rook, allowing 3.Qxe3. 1...Re6 unguards e6, which White exploits by 2.gxf8S, forking e6 and g6. 1...Re4 prevents a knight move to e4, and White continues 2.Sf1, threat 3.Qg3. 1...Bb7 unpins the rook directly for 2.Rd4+ with mate to follow by 3.Sd3 or 3.Qxe3, while 1...Sb5 unguards e4 for 2.Bxe5+ any 3.Qxe3. Finally the selfblock 1...fxg5 or hxg5 frees the queen from its guard of g5 for the pin-mate 2.Qf1+ Kg3 3.Qf2